Strange solar water heaters popular in Mexico ... Do they work?

I have a lot of homeowner experience in plumbing and electrical and a friend in Mexico recently asked my opinion on a solar hot water heater system being sold in Mexico and I couldn't properly respond. Most of the types of solar water heating cells I am familiar with and have seen used extensively in the US are flat panels with a glass cover with a black pipe weaving behind the glass and surrounded by a box to provide insulation and heat retention, usually shaped about 6" or so thick and around 2 x 4'. I understand how these work but my friend says they use a different type in Mexico. On a recent trip to Mexico I saw only these new styles he had described being used on rooftops and none of the flat panel models I was familiar with from the US. The Mexico units look like a chrome tank with a bunch of chrome metal rods sticking out. How do they work or do they work at all?

As these MX style heaters seem to be designed, there doesn't appear to be any way that they collect heat and keep it internal to the storage tank (if the attached large chrome cylinder is indeed a storage tank). Looking online, I couldn't find much information about them. All I could find referencing was on this link http://www.ecovita.mx/Web/Calentadores-Solares.aspx . Now my question is, do these even work or do they work well or how do these style collectors compare to the flat panel collectors that everyone in the US seems to use?

While continuing to search for an internal diagram or info on the MX style operation I ran into a similar looking tubular and tank design which shows the US model with a tank with tubes which are glass tubes with a vacuum pumped between the glass and the black copper pipe that runs through the glass vacuum tubes. These obviously work on the same principals as the flat panels, only with a much better vacuum insulator.

So what's with the Mexico models that have rods coming out of the tank that appear to be made of chrome, black or polished metal? Is this a "for show" device that has no real collection and heat retention potential, or am I missing something? Are perhaps the rods on these units also made of glass and just look chrome or metal from afar? If they are indeed metal, the physics of the design just doesn't pan out.

Re: [DonJuane] Strange solar water heaters popular in Mexico ... Do they work?

They work beautifully and are available in many sizes. We bought a 160 Liter model, good for 3-5 people, and never used our gas heater again. The 160 L tank is stainless and insulated, receiving cold water and producing very hot water. In fact, we had to loosen the pressure valve to vent sooner, or we would get live steam. The tubes are evacuated glass, in our model, with a copper rod inside. They contact a copper mass inside the tank, which heats the water. Other styles have water filled tubes, but if hail should break one water would flow out; not so with evacuated tubes and a tank made for higher pressures, as in our model (ACAL), supplied by e2energias. Of course, ours was installed on a flat roof, with the tank supported on a stand and the tubes slanting downward, and our location at Chapala, Jalisco never has freezing temperatures; all plumbing was on the roof, as is common there. I suspect that the type you are familiar with must feed to a conventional hot water heater, providing supplemental heat when the sun shines, but only when hot water is being used. Not nearly as efficient, unless it is pumped to recirculate through that tank and controlled by a temperature sensor arrangement.

Re: [jreboll] Strange solar water heaters popular in Mexico ... Do they work?

I have not seen that type in the USA either. If you send me your e-mail address by PM, I will send you a copy of the information that I have on file, but I cannot get it to post here. Click on my username and follow the clues to send a private message.

Re: [rvgringo] Strange solar water heaters popular in Mexico ... Do they work?

I had one in a rental house in Jocotepec. Really worked great until a kid broke a tube with a rock. I suggest you hide them. Landlord replaced it with a small gas heater Sparks Mexico Blog - Sparks Costalegre

Re: [sparks] Strange solar water heaters popular in Mexico ... Do they work?

Ours had evacuated heat tubes, which do not contain water. They have copper rods inside and contact a copper buss bar in the tank, which heats the water. So, a broken tube would not cause a water leak. The tank is a pressure vessel. There are less expensive units, with water filled tubes and non-pressure tanks, which are used for simple gravity systems.